St Petkov Petko, Vayssilov Georgi N, Krüger Sven, Rösch Notker
Faculty of Chemistry, University of Sofia, 1126 Sofia, Bulgaria.
Phys Chem Chem Phys. 2006 Mar 21;8(11):1282-91. doi: 10.1039/b518175e. Epub 2006 Feb 16.
Using a gradient-corrected density functional method, we studied computationally how single impurity atoms affect the structure and the properties of a Ni4 cluster. H and O atoms coordinate at a Ni-Ni bond, inducing small changes to the structure of bare Ni4 which is essentially a tetrahedron. For a C impurity, we found three stable structures at a Ni4 cluster. In the most stable geometry, the carbon atom cleaves a Ni-Ni bond of Ni4, binding to all Ni atoms. Inclusion of the impurity atom leads to a partial oxidation of the metal atoms and, in the most stable structures, reduces the spin polarization of the cluster compared to bare Ni4. An H impurity interacts mainly with the Ni 4s orbitals, whereas the Ni 3d orbitals participate strongly in the bonding with O and C impurity atoms. For these impurity atoms, Ni 3d contributions dominate the character of the HOMO of the ligated cluster, in contrast to the HOMO of bare Ni4 where Ni 4s orbitals prevail. We also discuss a simple model which relates the effect of a H impurity on the magnetic state of metal clusters to the spin character (minority or majority) of the LUMO or HOMO of the bare metal cluster.
我们使用梯度校正密度泛函方法，通过计算研究了单个杂质原子如何影响Ni4团簇的结构和性质。H原子和O原子配位在Ni-Ni键处，对基本呈四面体结构的裸Ni4结构产生微小变化。对于C杂质，我们在Ni4团簇中发现了三种稳定结构。在最稳定的几何结构中，碳原子切断了Ni4的一个Ni-Ni键，并与所有Ni原子结合。杂质原子的加入导致金属原子部分氧化，并且在最稳定的结构中，与裸Ni4相比，团簇的自旋极化降低。H杂质主要与Ni的4s轨道相互作用，而Ni的3d轨道在与O和C杂质原子的成键中起重要作用。对于这些杂质原子，与裸Ni4的HOMO中Ni的4s轨道占主导不同，Ni的3d贡献在配位团簇的HOMO特征中占主导。我们还讨论了一个简单模型，该模型将H杂质对金属团簇磁态的影响与裸金属团簇的LUMO或HOMO的自旋特征（少数或多数）联系起来。
